Unexpected Stereoselective Access to 2‐Aminooxazolines from Propargyl Ureas by Silver Salts under Mild Conditions
作者:Aleksandr Voronov、Alessandra Casnati、Paolo P. Mazzeo、Paolo Pelagatti、Alessia Bacchi、Raffaella Mancuso、Bartolo Gabriele、Elena Motti、Giovanni Maestri、Péter Pál Fehér、András Stirling、Nicola Della Ca'
DOI:10.1002/adsc.202200950
日期:——
Propargyl ureas can lead to a range of possible heterocyclic compounds, mainly depending on the employed catalyst. Silver salts are known to promote the N-5-exo-dig cyclization mode to imidazolidinone derivatives. Conversely, a versatile and stereoselective O-5-exo-dig cyclization of propargyl ureas to 2-aminooxazolines by Ag(I) catalysis is here disclosed. Good to excellent yields and complete stereoselectivity
炔丙基脲可导致一系列可能的杂环化合物,主要取决于所使用的催化剂。已知银盐促进N -5 -exo-dig环化模式生成咪唑啉酮衍生物。相反,此处公开了通过 Ag(I) 催化将炔丙基脲生成 2-氨基恶唑啉的多功能和立体选择性O -5-外切环化。在较温和的反应条件 (50–60 °C) 下,已经实现了良好到极好的收率和外部双键的完全立体选择性。还开发了从相应的炔丙基胺和异氰酸酯开始的一锅法方案。N , N '-二炔丙基脲经历了罕见的O-5- exo-dig/N -5 -endo-dig双环化序列。最后,提供了对 2-氨基恶唑的互变异构平衡及其相对反应性的见解。